1. Technical Field
The present invention relates to epitaxial films in general, and in particular to a method for growing germanium epitaxial films on silicon substrates.
2. Description of Related Art
There are two conventional methods for growing single-crystal germanium films on silicon substrates using ultra-high vacuum chemical vapor deposition (UHV-CVD). The first method allows a germanium film to be grown directly on top of a silicon layer, and the second method uses a silicon and silicon germanium buffer layer at the interface.
Since the first method is very selective, a germanium film only grows on a silicon layer and not on any exposed dielectric material. The problem with the first method is that the resultant germanium film is very rough and has a substantially high defect density. Compared with the first method, the second method is not selective at all. Thus, although the second method overcomes the roughness problem, the resultant germanium film occurs on an underlying silicon layer as well as an underlying dielectric layer. The growth on the underlying silicon layer is desired but the growth on the underlying dielectric layer is not.
The present disclosure provides an improved method for growing selective germanium epitaxial films.